// 将base64转换为blob
export function dataURLtoBlob(dataurl) {
    let arr = dataurl.split(","),
      mime = arr[0].match(/:(.*?);/)[1],
      bstr = atob(arr[1]),
      n = bstr.length,
      u8arr = new Uint8Array(n);
    while (n--) {
      u8arr[n] = bstr.charCodeAt(n);
    }
    return new Blob([u8arr], { type: mime });
}
  // 将blob转换为file
export function blobToFile(theBlob, fileName) {
    theBlob.lastModifiedDate = new Date();
    theBlob.name = fileName;
    return theBlob;
}